Truncated Conical PVDF Film Transducer for Air Ultrasound

In this paper, a truncated conical polyvinylidene fluoride (PVDF) film transducer for air ultrasound is investigated. The transducer was designed and fabricated using two identical pieces of fan-shaped PVDF film that makes the curve direction as consistent as possible with the molecular orientation direction of the film. The transducer has a truncated conical geometry, which provides a wide bandwidth with wide vertical beam angle. Measurements of the frequency response of transmitter output, angular performance, and pulse response are presented. The results show that the radiation directivity pattern of the transducer is in the axial direction of the conical film and the beam width is 140 degrees at -6dB level, which is more than that of the commercial 40-kHz ceramic transducers and cylindrical PVDF transducers. Therefore, this ultrasonic transducer is well-suited for three-dimensional (3D) ultrasonic positioning systems, and in particular for mounting at the conical head of electronic pens as an ultrasonic position transmitter.